JP6540796B2 - Piezoelectric element and ultrasonic sensor comprising the same - Google Patents

Description

  The present invention relates to a piezoelectric element and an ultrasonic sensor provided with the same.

  A general ultrasonic sensor constitutes a unimorph structure by bonding a piezoelectric element to the inner bottom surface of a case, and transmits and receives ultrasonic waves by bending the bottom of the case. The ultrasonic sensor provided with the lamination-type piezoelectric element is disclosed by Unexamined-Japanese-Patent No. 2002-204497 (patent document 1).

JP 2002-204497 A

  A plurality of electrodes are provided on the top surface of the piezoelectric element joined to the inner bottom surface of the case. When bonding an FPC or the like to the upper surface of the piezoelectric element, generally, electrical connections are individually made to a plurality of electrodes, but in practice, they are attached to one electrode of the upper surface of the piezoelectric element In some cases, a short circuit may occur due to the conductive material to be soldered, for example, the solder overflowing in the desired area and coming into contact with another adjacent electrode.

  Then, an object of this invention is to provide the piezoelectric element and ultrasonic sensor which reduced the probability that the short circuit by overflowing the electrically-conductive material used for joining may occur.

  In order to achieve the above object, a piezoelectric element according to the present invention is a stack of a plurality of piezoelectric layers, and has a laminate having a first main surface and a second main surface facing in opposite directions along the stacking direction. The laminate includes a transmitting unit, a receiving unit, and a separating unit separating the transmitting unit and the receiving unit from each other, and a transmission electrode covering the region corresponding to the transmitting unit on the first main surface And the receiving electrode is disposed so as to cover the region corresponding to the receiving portion in the first main surface, and the transmitting electrode is disposed in the inside of the laminate or the second main surface. The receiving electrode sandwiches at least a portion of the plurality of piezoelectric layers together with the conductive film, and the receiving electrode is configured of the plurality of piezoelectric layers together with the conductive film disposed on the inside or the second main surface of the laminate. At least a portion of our At least a part of the region corresponding to the separation portion in the first main surface is concaved or compared with the region in which the transmission electrode is arranged in the first main surface and the region in which the reception electrode is arranged. It is convex.

  In the above invention, preferably, the transmission unit and the reception unit include a structure in which piezoelectric layers and a conductor film are alternately disposed in the inside, and the separation unit is planarly viewed along the stacking direction. At times, it contains a part that does not contain a conductor film inside.

  In the above invention, preferably, the case includes a bottomed cylindrical case, the above-described piezoelectric element joined so that the second main surface is opposed to the inner bottom surface of the case, and a plurality of wirings; And a wiring lead-out component joined to the first main surface such that the wiring of the above is electrically connected to the reception electrode and the transmission electrode individually.

  In the above invention, preferably, the wiring lead-out component is joined to the first main surface by an anisotropic conductive adhesive.

  In the above invention, preferably, the anisotropic conductive adhesive contains a solder.

  According to the present invention, it is possible to realize a piezoelectric element and an ultrasonic sensor in which the probability of the occurrence of a short circuit due to the overflow of a conductive material used for bonding is reduced.

It is a functional block diagram of a sensor apparatus provided with the ultrasonic sensor in Embodiment 1 based on the present invention. It is sectional drawing of the ultrasonic sensor in Embodiment 1 based on this invention. It is a top view which shows the state which joined FPC to the piezoelectric element in Embodiment 1 based on this invention. It is a top view of the piezoelectric element in Embodiment 1 based on this invention. It is a perspective view of the piezoelectric element in Embodiment 1 based on this invention. It is the perspective view which also showed the internal structure of the piezoelectric element in Embodiment 1 based on this invention. It is explanatory drawing of the combination of the various electrodes with which the piezoelectric element in Embodiment 1 based on this invention is equipped. It is arrow sectional drawing regarding the VIII-VIII line in FIG. It is arrow sectional drawing regarding the IX-IX line in FIG. It is arrow sectional drawing regarding XX in FIG. It is explanatory drawing which gave hatching to the area | region where 1st main surface is concave in the top view of the piezoelectric element in Embodiment 1 based on this invention. It is a 1st fragmentary sectional view of the bonding interface vicinity of the piezoelectric element in embodiment 1 based on this invention, and FPC. It is a 2nd fragmentary sectional view of the junction interface vicinity of the piezoelectric element in embodiment 1 based on this invention, and FPC. It is 1st sectional drawing of the piezoelectric element in Embodiment 2 based on this invention. It is 2nd sectional drawing of the piezoelectric element in Embodiment 2 based on this invention. It is 3rd sectional drawing of the piezoelectric element in Embodiment 2 based on this invention. It is a fragmentary sectional view of the bonded interface vicinity of the piezoelectric element and FPC in Embodiment 2 based on this invention. It is sectional drawing of the piezoelectric element in Embodiment 3 based on this invention. It is sectional drawing of the piezoelectric element in Embodiment 4 based on this invention. It is 1st explanatory drawing of the clearance gap between the electrodes of the piezoelectric element based on this invention. It is 2nd explanatory drawing of the clearance gap between the electrodes of the piezoelectric element based on this invention. It is a perspective view of an example of a 3 terminal type piezoelectric element. FIG. 23 is a perspective view of a state in which the piezoelectric element is turned over from the state shown in FIG. 22. It is a typical sectional view of an example of a 3 terminal type piezoelectric element. It is a perspective view of an example of a 4 terminal type piezoelectric element. FIG. 26 is a perspective view of a state in which the piezoelectric element is turned over from the state shown in FIG. 25. FIG. 2 is a schematic cross-sectional view of an example of a four-terminal type piezoelectric element. It is a functional block diagram of a sensor apparatus provided with the ultrasonic sensor in Embodiment 5 based on this invention.

  Hereinafter, an embodiment based on the present invention will be described with reference to the drawings. When the number, the amount, and the like are mentioned, the scope of the present invention is not necessarily limited to the number, the amount, and the like unless otherwise specified. The same parts and corresponding parts are denoted by the same reference numerals, and redundant description may not be repeated.

Embodiment 1
FIG. 1 is a diagram showing functional blocks of a sensor device 1 provided with the ultrasonic sensor 100 according to the first embodiment. The sensor device 1 includes an ultrasonic sensor 100, a microcomputer 101, a memory 102, a detection circuit 103, a signal generation circuit 104, a power supply 105, and a reception amplifier 106. The ultrasonic sensor 100 includes a piezoelectric element 50, which has a three-terminal structure including electrodes 10, 20, and 30.

  The microcomputer 101 reads data stored in the memory 102 and outputs a control signal to the signal generation circuit 104. The signal generation circuit 104 generates an AC voltage from the DC voltage based on the control signal. The alternating voltage is supplied to the ultrasonic sensor 100, and ultrasonic waves are transmitted (transmitted) from the ultrasonic sensor 100 to the air or the like. When the ultrasonic sensor 100 receives a reflected wave from a target, a received wave signal generated by the ultrasonic sensor 100 is sent as a voltage value to the receiving amplifier 106 and input to the microcomputer 101 through the detection circuit 103. The microcomputer 101 makes it possible to grasp information regarding the presence or movement of a target.

(Ultrasonic sensor 100)
FIG. 2 is a cross-sectional view showing the ultrasonic sensor 100 in the first embodiment. The ultrasonic sensor 100 includes a piezoelectric element 50, a case 60, a sound absorbing material 63, an adhesive 64, a bonding agent 65, fillers 71 and 72, and an FPC (Flexible Printed Circuits) 80. The case 60 is conductive and formed in a bottomed cylindrical shape. The case 60 is made of, for example, highly elastic and lightweight aluminum. Case 60 is produced by, for example, forging or cutting such aluminum.

  The case 60 includes a disc-shaped bottom portion 62 and a cylindrical tubular portion 61 provided along the periphery of the bottom portion 62. The bottom portion 62 has an inner bottom surface 62S and an outer surface 62T. The piezoelectric element 50 is made of, for example, a lead zirconate titanate ceramic. The piezoelectric element 50 is disposed on the inner bottom surface 62S of the bottom portion 62, and is bonded to the inner bottom surface 62S using an adhesive 64. The adhesive 64 is, for example, an epoxy adhesive. When the ultrasonic sensor 100 is driven, the piezoelectric element 50 bends together with the bottom portion 62.

  The piezoelectric element 50 has three electrodes (not shown) (portions corresponding to the electrodes 10 to 30 in FIG. 1; details will be described later). As shown in FIG. 3, the tip 80T of the FPC 80 has, for example, a T-shape. The FPC 80 is electrically bonded to these electrodes via the bonding agent 65. As the bonding agent 65, for example, a resin material to which a metal is added is used. The portion of the FPC 80 opposite to the portion joined to the piezoelectric element 50 is taken out of the case 60 and electrically connected to the signal generation circuit 104 (FIG. 1) and the receiving amplifier 106 (FIG. 1). It is done.

(Piezoelectric element 50)
FIG. 3 is a plan view showing the piezoelectric element 50 and the FPC 80. As shown in FIG. FIG. 4 is a plan view showing the piezoelectric element 50 (in a state in which the FPC 80 is removed). FIG. 5 is a perspective view showing the piezoelectric element 50. As shown in FIG. FIG. 6 is a perspective view showing the piezoelectric element 50 and its internal structure. FIG. 7 is an explanatory view of a combination of the electrodes 10, 20, and 30 provided on the piezoelectric element 50. As shown in FIG. FIG. 8 is a cross-sectional view taken along line VIII-VIII in FIG. FIG. 9 is a sectional view taken along the line IX-IX in FIG. FIG. 10 is a sectional view taken along the line X-X in FIG.

  In FIGS. 3 to 10, arrows X, Y and Z are shown for the convenience of description. Arrows X, Y, Z have a mutually orthogonal relationship. Hereinafter, each configuration of the piezoelectric element 50 may be described with reference to arrows X, Y, and Z. However, the arrangement relationship of each configuration (feature related to orthogonal and parallel) is not limited to the arrangement shown by arrows X, Y, and Z. It is not limited to the relationship. The same applies to FIGS. 11 to 16 described later.

  As shown in FIGS. 3 to 10, the piezoelectric element 50 is a laminated piezoelectric element, and is attached to the inner bottom surface 62S of the case 60 using an adhesive 64. The piezoelectric element 50 has a rectangular parallelepiped shape having a longitudinal direction and a lateral direction. Specifically, the piezoelectric element 50 includes a piezoelectric layer 40 (FIGS. 3 to 6, FIGS. 8 to 10), an electrode 10 (FIG. 7), an electrode 20 (FIG. 7), and an electrode 30 (FIG. 7). And). The outer shape of the piezoelectric layer 40 is a substantially rectangular parallelepiped (see FIGS. 5 and 6), and the piezoelectric layer 40 has an upper surface 41, side surfaces 42 to 45, and a lower surface 46.

  The upper surface 41 is a main surface facing in one direction along the stacking direction of the piezoelectric element 50, and is a surface of the piezoelectric layer 40 located on the side of the arrow Z direction, and the lower surface 46 is a piezoelectric layer 40. Is a surface located on the side opposite to the arrow Z direction. The side surfaces 42 and 44 are surfaces of the piezoelectric layer 40 orthogonal to the arrow X direction, and have a positional relationship of facing each other. The side surfaces 43 and 45 are surfaces of the piezoelectric layer 40 orthogonal to the arrow Y direction, and have a positional relationship in which they face each other.

(Electrode 10 (reception electrode))
The electrode 10 includes a disc portion 11 and an extension portion 12 (see FIG. 7). The electrode 10 functions as a receiving electrode. The extending portion 12 has a shape extending outward from the outer edge of the disc portion 11. The extension portion 12 is arranged to extend from the side where the disc portion 11 is located toward the side where the side surface 42 of the piezoelectric layer 40 is located. As shown in FIG. 3, the electrode 10 and the FPC 80 (wiring pattern 81) are electrically connected in a portion (connection portion 10C) between the wiring pattern 81 provided on the FPC 80 and the extending portion 12 of the electrode 10 (See also FIG. 4 and FIG. 5).

(Electrode 20 (transmission electrode))
The electrode 20 includes an end face 21, an upper face 22, and middle parts 23 and 24 (see FIG. 7). The electrode 20 functions as a transmission electrode. That is, by applying an alternating voltage between the electrodes 20 and 30, the electrode 20 forms a potential difference with the electrode 30. The end face 21 faces the side surface 42 (FIG. 5) of the piezoelectric layer 40 and contacts the side surface 42. The end 21T of the end face 21 is a portion located on the side of the adhesive surface of the electrode 20 (the side of the adhesive 64). The end 21T has a shape extending along a portion of the lower end of the side surface 42 in the longitudinal direction of the piezoelectric element 50.

  The upper surface 22 of the electrode 20 is connected to the end of the end surface 21 in the direction of the arrow Z, and is disposed on the upper surface 41 of the piezoelectric layer 40. The intermediate portions 23 and 24 are portions of the electrode 20 disposed inside the piezoelectric layer 40, and they are not visually recognized when the piezoelectric element 50 is completed (see FIG. 5). The intermediate portion 33 of the electrode 30 is disposed between the intermediate portion 23 and the intermediate portion 24 (see FIGS. 8 to 10 and the like). In the example illustrated here, the intermediate portions 23 and 24 are described as a configuration that can not be viewed from the outside of the piezoelectric element 50, but one or both of the intermediate portions 23 and 24 can be viewed from the outside It may be.

  On the inner side of the intermediate portions 23, 24, hollow portions 23H, 24H (FIG. 7) and notches 23T, 24T are respectively provided. As shown in FIGS. 7 and 9, the end of the intermediate portions 23 and 24 in the opposite direction to the arrow X (specifically, the end on the side where the end face 21 is located) Connected On the other hand, the end portions of the intermediate portions 23 and 24 in the arrow X direction are not connected to the end surface portion 31 of the electrode 30 described later, and are separated from the end surface portion 31. As shown in FIG. 3, in a portion (connection portion 20C) between the wiring pattern 82 provided on the FPC 80 and the upper surface portion 22 of the electrode 20, the electrode 20 and the FPC 80 (wiring pattern 82) are electrically connected. (See also Figure 4 and Figure 5).

(Electrode 30)
The electrode 30 as the ground electrode includes an end surface portion 31, an upper surface portion 32, a middle portion 33, and a lower surface portion 34 (see FIG. 7). The electrode 30 functions as a common electrode. The end face 31 faces the side surface 44 (FIG. 5) of the piezoelectric layer 40 and is in contact with the side surface 44. The lower surface portion 34 faces the lower surface 46 of the piezoelectric layer 40 and is in contact with the lower surface 46. The upper surface portion 32 is continuously provided at the end of the end surface portion 31 in the direction of the arrow Z, and is disposed on the upper surface 41 of the piezoelectric layer 40. The intermediate portion 33 is a portion of the electrode 30 which is disposed inside the piezoelectric layer 40, and the intermediate portion 33 is not visually recognized when the piezoelectric element 50 is completed (see FIG. 5). In the example illustrated here, the intermediate portion 33 is described as being not visible from the outside of the piezoelectric element 50, but the intermediate portion 33 may be configured to be visible from the outside.

  On the inside of the upper surface portion 32 and the middle portion 33, hollow portions 32H and 33H (FIG. 7) are provided, respectively. The disc portion 11 of the electrode 10 is disposed inside the hollow portion 32H (see FIG. 5). Notches 32T and 33T are also provided inside the upper surface portion 32 and the middle portion 33, respectively. The extension 12 of the electrode 10 is disposed inside the notch 32T (see FIG. 5). A receding portion 32F is provided in a portion of the upper surface portion 32 in the direction opposite to the arrow Y. The receding portion 32F is a portion for permitting the arrangement of the upper surface portion 22 of the electrode 20.

  As shown in FIGS. 7 and 9, the end portions of the upper surface portion 32, the intermediate portion 33 and the lower surface portion 34 in the arrow X direction are connected to the end surface portion 31. On the other hand, the end of the upper surface 32, the intermediate portion 33 and the lower surface 34 in the direction opposite to the arrow X is not connected to the end surface 21 of the electrode 20 and is separated from the end surface 21. As shown in FIG. 3, in the portion (connection portion 30C) between the wiring pattern 83 provided on the FPC 80 and the upper surface portion 32 of the electrode 30, the electrode 30 and the FPC 80 (wiring pattern 83) are electrically connected. (See also Figure 4 and Figure 5).

(Transmitter and receiver)
Referring to FIGS. 8 to 10, a transmitter 40N and a receiver 40M are formed inside the piezoelectric layer 40. The transmitter 40N has a four-layer structure including first unit piezoelectric layers N1 to N4. The first unit piezoelectric layers N <b> 1 to N <b> 4 are stacked in a direction away from the bottom portion 62 of the case 60 and electrically connected in parallel by the electrodes 20 and 30. The white arrows in FIGS. 8 to 10 indicate the polarization directions of the respective piezoelectric layers. On the other hand, the receiving unit 40M has a single-layer structure of the second unit piezoelectric layer M1.

  The lower surface portion 34 of the electrode 30 has a shape that extends to both the transmitter 40N and the receiver 40M. The upper surface portion 22 of the electrode 20 is opposed to the lower surface portion 34 of the electrode 30 with the transmitter 40N including the first unit piezoelectric layers N1 to N4 interposed therebetween. The disc portion 11 of the electrode 10 is opposed to the lower surface portion 34 of the electrode 30 with the receiving portion 40M including the second unit piezoelectric layer M1 interposed therebetween.

  That is, in the piezoelectric layer 40, a region located between the upper surface 22 of the electrode 20 and the lower surface 34 of the electrode 30, a region located between the intermediate region 23 of the electrode 20 and the upper surface 32 of the electrode 30 The region located between the middle portion 23 of the electrode 20 and the lower surface portion 34 of the electrode 30 functions as a transmitter 40N. On the other hand, in the piezoelectric layer 40, a region located between the disc portion 11 of the electrode 10 and the lower surface portion 34 of the electrode 30 functions as the receiving portion 40M.

  As shown in FIGS. 8 and 10, the transmitter 40N and the receiver 40M are formed adjacent to each other in the surface direction (X-Y plane direction) of the inner bottom surface 62S of the bottom portion 62 of the case 60. Specifically, the receiving unit 40M is provided in the center of the piezoelectric layer 40, and the transmitting unit 40N is provided in the peripheral portion which is the outer side in the radial direction than the receiving unit 40M so as to surround the receiving unit 40M. It is done.

  As shown in FIGS. 9 and 10, in the piezoelectric element 50, the lower surface of the electrode 30 is on the side of the adhesive surface of the piezoelectric element 50 (the side of the surface of the piezoelectric element 50 to be adhered to the bottom 62 of the case 60). The portion 34 and the end 21T of the end face 21 of the electrode 20 are located. The lower surface portion 34 of the electrode 30 is attached to the bottom portion 62 (inner bottom surface 62S) of the case 60 with an adhesive 64. As described above, the application of an alternating voltage between the electrodes 20 and 30 causes the electrode 20 to form a potential difference with the electrode 30. Thereby, the ultrasonic sensor 100 can transmit ultrasonic waves. While transmitting an ultrasonic wave, an alternating voltage is applied to the electrode 30, but while receiving an ultrasonic wave, the potential of the electrode 30 is 0 volt. Thus, the ultrasonic sensor 100 can receive ultrasonic waves.

  As shown in FIGS. 8 and 10, the portion of the upper surface 41 of the piezoelectric layer 40 exposed between the electrode 10 and the electrode 30 is recessed. The part which mutually isolate | separates the receiving part 40M and the transmission part 40N among laminated bodies corresponds to a isolation | separation part. The area where the upper surface 41 is recessed is at least a part of the area corresponding to the separation portion. The upper surface of the piezoelectric layer 40 in FIGS. 8 to 10 corresponds to the “first main surface”, and the lower surface corresponds to the “second main surface”.

  The piezoelectric element 50 in the present embodiment is formed by laminating a plurality of piezoelectric layers, and has an upper surface 41 as a first main surface and a lower surface 46 as a second main surface, which are opposite to each other along the stacking direction. It has a laminate. The laminate includes a transmitting unit 40N, a receiving unit 40M, and a separating unit that separates the transmitting unit 40N from the receiving unit 40M. An electrode 30 as a transmission electrode is disposed to cover a region of the first main surface (upper surface 41) corresponding to the transmission unit 40N. An electrode 10 as a receiving electrode is disposed to cover a region of the first main surface (upper surface 41) corresponding to the receiving unit 40M. The transmission electrode (electrode 30) sandwiches at least a part of the plurality of piezoelectric layers together with the conductor film disposed in the interior of the laminate or on the second major surface (the lower surface 46). The receiving electrode (electrode 10) sandwiches at least a part of the plurality of piezoelectric layers together with the conductor film disposed in the interior of the laminate or on the second major surface (lower surface 46). In at least a part of the region corresponding to the separation portion in the first main surface (upper surface 41), the region in which the transmission electrode (electrode 30) is arranged in the first main surface and the reception electrode (electrode 10) are arranged It is concave or convex compared to the Here, although it is referred to as “concave or convex”, in the example shown in FIGS. 8 and 10, at least a part of the region corresponding to the above-described separation portion is concave. A plan view of the piezoelectric element 50 is already shown in FIG. 4, but FIG. 11 shows a hatched area in the plan view where the first main surface is concave. The area between the electrode 10 and the electrode 30 is concave. This is an area corresponding to the separation unit. On the other hand, in the region between the electrode 20 and the electrode 30, the first major surface is not concave.

  A partial cross-sectional view in the vicinity of the interface in a state where the FPC 80 is bonded to the upper surface of the piezoelectric element 50 in the present embodiment is shown in FIG. The electrode 10 and the electrode 30 are disposed on the first major surface of the laminate of the piezoelectric layer. A recess is formed in a region between the electrode 10 and the electrode 30 in the first major surface of the laminate. Wiring patterns 81 and 83 are provided on the surface of the FPC 80. Bonding between the upper surface of the piezoelectric element 50 and the FPC 80 is performed by an anisotropic conductive adhesive. Anisotropic conductive adhesive is one in which solder particles are mixed in a resin as an adhesive, and by bonding, the solder particles agglomerate in the vicinity of an electrode made of metal to make an electrical connection. Is the thing to be done. In the example shown in FIG. 12, it can be seen that the solder joints 67 are formed in two places. The solder joints 67 are each formed by aggregation and melting of the solder particles. The electrode 10 is electrically connected to the wiring pattern 81 by the solder joint portion 67, and the electrode 30 is electrically connected to the wiring pattern 83. Since a recess is formed between the electrode 10 and the electrode 30, the distance along the surface of the laminate is longer than in the case where there is no recess. This reduces the probability that the solder joint 67 will reach the next undesired electrode.

  Further, as shown in FIG. 13, even if the solder particles 68 do not adhere to the electrode 10 and overflow to the side, the solder particles 68 are accommodated in the recess, so the solder particles reach the next electrode 30. The probability is reduced.

Second Embodiment
The configuration of the piezoelectric element 50A included in the ultrasonic sensor 100 according to the second embodiment is basically the same as that described in the first embodiment, but differs in the following points.

  In the piezoelectric element 50A according to the present embodiment, cross-sectional views corresponding to FIGS. 8 to 10 of the first embodiment are respectively shown in FIGS.

  In the present embodiment, at least a part of the region corresponding to the separation portion in the first main surface (upper surface 41) is the region where the transmission electrode (electrode 30) is disposed in the first main surface and the reception electrode (the It is convex compared with the area | region where the electrode 10) is arrange | positioned. The hatched area in FIG. 11 of the first main surface is convex. That is, the region between the electrode 10 and the electrode 30 is convex. This is an area corresponding to the separation unit. On the other hand, in the region between the electrode 20 and the electrode 30, the first major surface is not convex.

  A partial cross-sectional view in the vicinity of the interface in a state in which the FPC 80 is bonded to the upper surface of the piezoelectric element 50A in the present embodiment is shown in FIG. A convex portion is formed in a region between the electrode 10 and the electrode 30 in the first main surface of the laminate. Since the projection is formed between the electrode 10 and the electrode 30 in this manner, the distance along the surface of the laminate is longer than in the case where there is no projection. This reduces the probability that the solder joint 67 will reach the next undesired electrode. Further, as shown in FIG. 17, even if the solder does not adhere to the electrode 10 and overflows to the side, since the solder is blocked by the convex portion, the probability of the solder reaching the adjacent electrode 30 is reduced.

  In addition, the recessed part or convex part shown in Embodiment 1, 2 may be formed by arbitrary methods. For example, you may form an unevenness | corrugation in the upper surface of a laminated body by stamping using the type | mold with which the unevenness | corrugation was previously provided. Alternatively, the recess may be formed by performing some removal process on the upper surface.

  In the first and second embodiments, the conductive material used for the electrical connection with the FPC 80 is the solder, but this is merely an example. The conductive material is not limited to solder, and may be another material.

Third Embodiment
The configuration of the piezoelectric element 50B included in the ultrasonic sensor 100 according to the third embodiment is basically the same as that described in the first embodiment, but differs in the following points.

  In piezoelectric element 50B in the present embodiment, as shown in FIG. 18, a recess is formed in a region corresponding to the separation portion in upper surface 41 as the first main surface of the laminate, and in receiving portion 40M, Internal electrodes 75, 76, 77 are arranged. The internal electrodes 75, 76, and 77 may be dummy electrodes or may be electrodes having some functions.

Embodiment 4
The configuration of the piezoelectric element 50C included in the ultrasonic sensor 100 according to the fourth embodiment is basically the same as that described in the second embodiment, but differs in the following points.

  In piezoelectric element 50C in the present embodiment, as shown in FIG. 19, in the region corresponding to the separation portion in upper surface 41 as the first main surface of the laminated body, a convex portion is formed, and in receiving portion 40M , Internal electrodes 75, 76, 77 are disposed. The internal electrodes 75, 76, and 77 may be dummy electrodes or may be electrodes having some functions.

  The third and fourth embodiments can be expressed as follows. The transmitting unit 40N and the receiving unit 40M in the piezoelectric element include a structure in which a piezoelectric layer and a conductor film are alternately arranged in the inside, and the separation unit is in the stacking direction (the first main surface (upper surface 41) When viewed in plan along the vertical direction), it includes a portion in which the conductive film is not included inside.

  In the third and fourth embodiments, using the deformation phenomenon brought about by the presence or absence of the internal electrode, a concave or a convex may be formed in a region corresponding to the separation portion in the upper surface 41 as the first main surface of the laminate. it can. In the third and fourth embodiments, the effects described in the first or second embodiment can be obtained by forming the concave or convex in this manner.

  In the examples shown in FIG. 12, FIG. 13 and FIG. 17, the entire gap between the electrodes disposed on the first main surface of the laminate is concave or convex. The entire gap need not be concave or convex. For example, as shown in FIGS. 20 and 21, a part of the gap may be concave or convex. Also in such a case, the same effects as those described in the first to fourth embodiments can be obtained. In FIGS. 20 and 21, the positions of the ends of the internal electrodes 76 and 77 and the positions of the ends of the electrode 10 are different. When the unevenness is formed on the first main surface of the laminate by using the presence or absence of the internal electrode, there is a tendency for a concave or a convex to be formed in the region where the internal electrode is not present. The region in which the concave or convex is formed due to this phenomenon may not coincide with the region viewed as a gap between the electrodes disposed on the first major surface. Such a positional relationship may result in a configuration in which a portion of the gap is concave or convex as shown in FIGS. 20 and 21, respectively. Even with such a configuration, the same effects as those described in the first to fourth embodiments can be obtained.

The present invention can be applied to various types of piezoelectric elements as shown below.
22 to 24 show a piezoelectric element 50D as an example of a three-terminal type piezoelectric element. As shown in FIG. 22, the three-terminal type piezoelectric element is a type in which the electrode 10, a part of the electrode 20D, and a part of the electrode 30D are disposed on the upper surface of the piezoelectric element 50D, ie, the first main surface. Say. In FIG. 22, the end face 21D of the electrode 20D and the top face 32D of the electrode 30D are shown. A state in which the state shown in FIG. 22 is reversed is shown in FIG. As shown in FIG. 23, most of the area of the lower surface, that is, the second main surface is covered by the electrode 20D. In FIG. 23, the lower surface portion 22D of the electrode 20D and the end surface portion 31D of the electrode 30D are shown. Furthermore, FIG. 24 shows a pseudo sectional view of the piezoelectric element 50D. However, FIG. 24 is not a cross-sectional view that actually appears by cutting straight at any point in FIG. 22, but for the convenience of description, the electrode 10, the electrode 20D, and the electrode 30D shown in FIG. The cross-sections of the part of are arranged in the same width and displayed in a pseudo manner. In FIG. 24, the separation between the electrode 10 and the electrode 20D is also shown. The separation between electrode 10 and electrode 30D is also shown. In the example shown in FIG. 24, a concave or a convex is formed in these separation portions.

  Although the three-terminal type piezoelectric element is illustrated here, the piezoelectric element is not limited to the three-terminal type. It may be of a type having three or more terminals.

25 to 26 show a piezoelectric element 50E as an example of a four-terminal type piezoelectric element. The four-terminal type piezoelectric element is a type in which the electrode 10, a part of the electrode 20A, a part of the electrode 20B, and a part of the electrode 30A are disposed on the top surface of the piezoelectric element 50E as shown in FIG. Say A state in which the state shown in FIG. 25 is reversed is shown in FIG. Most areas of the lower surface or second major surface as shown in FIG. 26 is covered by the electrodes 3 0A. Furthermore, FIG. 27 shows a pseudo cross section of the piezoelectric element 50E. FIG. 27 is a cross-sectional view in which three types of parts are arranged and displayed for convenience as in FIG. In the piezoelectric element 50E, the electrodes 20A and 20B correspond to transmission electrodes, respectively. The electrode 10 corresponds to a receiving electrode.

Fifth Embodiment
The ultrasonic sensor 200 in Embodiment 5 based on this invention is demonstrated. FIG. 28 is a diagram showing a functional block of a sensor device 1L provided with an ultrasonic sensor 200, and corresponds to FIG. 1 in the first embodiment. The ultrasonic sensor 200 includes a piezoelectric element 50E, and the piezoelectric element 50E has a four-terminal structure including the electrodes 10, 20A, 20B, and 30A. The electrodes 20A and 20B are connected to the signal generation circuit 104. The electrode 10 is connected to the reception amplifier 106, and the electrode 30A is grounded.

  As shown in FIG. 2, the ultrasonic sensor 100 in the present embodiment includes a case 60, a piezoelectric element 50, and an FPC 80. The case 60 is cylindrical with a bottom. The piezoelectric element 50 is bonded to the inner bottom surface 62S of the case 60 such that the second main surface faces the inner bottom surface 62S. The FPC 80 includes a plurality of wires. The FPC 80 is a wiring lead-out component joined to the first main surface such that the plurality of wirings are electrically connected individually to the reception electrode and the transmission electrode. The piezoelectric element 50 mentioned here is a piezoelectric element having the configuration described in any of the above embodiments.

  By adopting this configuration, the ultrasonic sensor 100 according to the present embodiment is an ultrasonic sensor in which the probability of occurrence of a short circuit due to the overflow of the conductive material at the junction between the piezoelectric element and the wiring lead component is reduced. Can.

  The wiring lead-out component is preferably joined to the first major surface (upper surface 41 of the laminate) by an anisotropic conductive adhesive. As described above, when an anisotropic conductive adhesive is used for bonding, the effect of reducing the probability of occurrence of a short circuit can be particularly remarkably achieved. Although FIG. 2 shows an example in which the wiring lead-out component is the FPC 80, the same is true even if the wiring lead-out component is another type of component.

  The anisotropic conductive adhesive preferably contains a solder. As described above, when the anisotropic conductive adhesive contains a solder as a conductive material, the effect of reducing the probability of occurrence of a short circuit can be particularly remarkably achieved.

Note that a plurality of the above embodiments may be appropriately combined and adopted.
In addition, the said embodiment disclosed this time is an illustration and restrictive at no points. The scope of the present invention is indicated not by the above description but by the scope of the claims, and includes all the modifications within the meaning and scope equivalent to the scope of the claims.

  1, 1 L sensor device, 10 electrodes (receiving electrode), 10C, 20C, 30C connection point, 11 disc portion, 20, 20A, 20B, 20D, 30D, 30 electrode, 21, 21D, 31D end face portion, 21T end portion 22 and 32D upper surface portion 22D lower surface portion 23 and 24 middle portion 23H and 24H hollow portion 23T and 24T notch portion 30A electrode (ground electrode) 31 end surface portion 32H and 33H hollow portion 32T and 33T Notched part, 33 middle part, 40 piezoelectric layer, 40 M receiver, 40 N transmitter, 41 upper surface of the piezoelectric layer, 42, 44 side surface of the piezoelectric layer, 46 lower surface, 50, 50A, 50B, 50C, 50D, 50E Piezoelectric element, 60 case, 61 cylindrical portion, 62 bottom, 62S inner bottom surface, 62T outer surface, 63 sound absorbing material, 64 adhesive, 65 Mixture, 67 solder joints, 68 solder particles, 69 resin parts, 71, 72 fillers, 75, 76, 77 internal electrodes, 80 FPC, 81, 82, 83 wiring patterns, 100, 200 ultrasonic sensors, 101 microcomputers , 102 memories, 103 detection circuits, 104 signal generation circuits, 105 power supplies, 106 reception amplifiers, N1 to N4 first unit piezoelectric layers, M1 second unit piezoelectric layers.

Claims (5)

It is a laminate of a plurality of piezoelectric layers, and has a laminate having a first main surface and a second main surface facing in opposite directions along the stacking direction.
The laminate includes a transmitting unit, a receiving unit, and a separating unit separating the transmitting unit and the receiving unit from each other,
A transmission electrode is disposed to cover a region corresponding to the transmission unit in the first main surface,
A receiving electrode is disposed to cover a region corresponding to the receiving portion on the first main surface,
The transmission electrode sandwiches at least a part of the plurality of piezoelectric layers together with a conductor film disposed in the inside of the laminate or on the second main surface,
The receiving electrode sandwiches at least a part of the plurality of piezoelectric layers together with a conductor film disposed in the interior of the laminate or on the second main surface,
At least a part of the area corresponding to the separation portion in the first main surface is convex compared to the area in which the transmission electrode is arranged in the first main surface and the area in which the reception electrode is arranged. It is a piezoelectric element. The transmitting unit and the receiving unit include a structure in which a piezoelectric layer and a conductor film are alternately disposed inside,
The piezoelectric element according to claim 1, wherein the separation portion includes a portion in which a conductive film is not included when viewed in plan along the stacking direction. Bottomed cylindrical case,
The piezoelectric element according to claim 1 or 2, wherein the second main surface is joined to face the inner bottom surface of the case.
And a wire lead-out component joined to the first main surface such that the plurality of wires are electrically connected to the reception electrode and the transmission electrode individually. Ultrasonic sensor.   The ultrasonic sensor according to claim 3, wherein the wiring lead-out component is bonded to the first main surface by an anisotropic conductive adhesive.   The ultrasonic sensor according to claim 4, wherein the anisotropic conductive adhesive comprises a solder.

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